1. Field of the Disclosure
The present disclosure relates to a bus bar of an EPS motor, and more particularly to a bus bar of an EPS motor configured to improve a terminal structure of a bus bar to enable an easy assembly between a stator and the bus bar, whereby assemblage and operational reliability can be enhanced.
The present disclosure further relates to a mold structure of a bus bar of an EPS motor, and more particularly to a mold structure of a bus bar of an EPS motor configured to fix position of a terminal in an insert molding process of bus bar by improving a terminal structure of the bus bar and to accurately maintain a mutual gap.
2. Discussion of the Related Art
Generally, almost every vehicle employs an electric power-assist steering system. Such an electric power-assist steering system generates an assist force based on the steering torque and the steering angle, so as to enhance the steering performance of the vehicle.
That is, a steering system that assists a steering force of a vehicle with a separate power is used to enhance the motion stability of a vehicle.
Conventionally, the auxiliary steering device uses hydraulic pressure, but an Electronic Power Steering (EPS) system adapted to transmit a rotation output of an electric motor to a steering shaft via a speed reduction mechanism has been increasingly employed these days from a viewpoint of a reduction in engine load, a reduction in weight, an enhanced steering stability and a quick restoring force.
The EPS system is such that an Electronic Control Unit (ECU) drives a motor in response to steering conditions detected by a speed sensor, a torque angle sensor and a torque sensor to enhance a steering stability and provide a quick restoring force, whereby a driver can safely steer a vehicle.
The EPS system is also such that a motor assists a torque manipulating a steering wheel to allow a driver to steer a vehicle with less power, where the motor employs a Brushless Direct Current (BLDC) motor.
The BLDC motors have been increasingly used because the brushless motors are excellent in maintenance property, have small size, and are capable of generating high torque. The BLDC motor is a DC motor mounted with an electronic rectifying system, excluding those mechanical contact portions such as a brush and a rectifier from the conventional DC motor. The BLDC motor largely includes a stator and a rotor, where the stator is wound with a coil, and the rotor is coupled to a magnet and rotated by electromagnetic interaction therebetween.
The stator includes a core and a coil, and generally employs a plurality of divided cores these days that are connected in a circular shape.
FIG. 1 is a perspective view illustrating a stator and a bus bar of an EPS motor.
The stator (10) is a member secured inside a housing (not shown) of a motor to generate a rotation movement in response to an electromagnetic interaction with a rotor (not shown) arranged inside a hollow hole, and includes a core (13) and a coil (11) wound on the core (13).
A motor in a vehicle generally uses a plurality of coils connected in parallel to reduce loss caused by coil resistance, as illustrated in FIG. 1. Thus, the coil in parallel connection is extended to input and output terminals from where the connection is integrally performed. In order to integrally connect the parallel arranged coil (11), a bus bar (20) is arranged at an upper side of the stator (10).
Each coil terminal (12) of respectively wound coils (11) is arranged on the upper side of the stator (10), where the bus bar (20) is connected to the coil terminal (12).
The bus bar (20) is securely arranged thereon with a plurality of metal materials electrically connected to the coil terminal (12) and insulated by an insulator (22). The bus bar (20) substantially takes the shape of a doughnut and correspondingly arranged on the upper side of the stator (10). A periphery of the bus bar (20) is arranged with a plurality of terminals (21) for connection with coil terminals (12).
FIG. 2 is a lateral view of the bus bar (20) thus configured.
FIG. 2 illustrates a three-phase circuit, where each input/output terminal is alternatively and sequentially arranged to the periphery of the bus bar (20).
FIG. 3 is a perspective view illustrating a bus bar of an EPS motor according to prior art.
The bus bar (20) substantially takes the shape of a doughnut and correspondingly arranged on the upper side of the stator (10). A periphery of the bus bar (20) is arranged with a plurality of terminals (21) for connection with coil terminals. The insulator (22) for securing each position of the terminals (21) insulates the metallic terminals (21) and forms a periphery of the bus bar (20).
FIG. 4 is a perspective view illustrating the bus bar of FIG. 1 excluded of an insulator.
Each terminal (21a, 21b, 21c, 21d) shows a different polarity at the three phase circuit. Terminals of same type are mutually connected by ring-shaped body units (12a, 12b, 12c, 12d). The body unit sequentially and circumferentially includes the first body unit (12a), the second body unit (12b), the third body unit (12c) and the fourth body unit (12d).
Each of the body units (12a, 12b, 12c, 12d) takes the shape of a thin ring, is insulated by the insulator (22) and secured to a position. The terminals (21a, 21b, 21c, 21d) and the body units (12a, 12b, 12c, 12d) are mutually insulated in a narrow space. The insulator (22) is arranged in a space formed by the terminals (21a, 21b, 21c, 21d) and the body units (12a, 12b, 12c, 12d), and insulates the terminals (21a, 21b, 21c, 21d) from the body units (12a, 12b, 12c, 12d).
The insulator (22) takes a shape by injection-molding a resin material after properly positioning the terminals (21a, 21b, 21c, 21d) and the body units (12a, 12b, 12c, 12d ) in a mold. 
Meanwhile, a dielectric breakdown in a product among terminals may be generated to result in imperfection in motor operation and defect affecting safety of an operator, if a predetermined gap is not maintained among the terminals during insert molding operation. Another problem is that the insert molding operation cannot be easily performed due to a tight gap among parts and materials of thin thickness.
Still another problem is that a spatial restriction is generated during welding operation of coil terminals (21) due to the tight gap among terminals (21), if the terminals (21) are arranged in the above manner. Still further problem is that an electrical insulation cannot be realized due to undesirable contact to welded portions among adjacent terminals (21) that is generated by the tight gap among terminals (21) in the welding operation.